The No. 8 Oregon State Beavers have been able to keep their undefeated record intact thus far, but they'll need their leader back under center to have a serious shot at the Pac-12 title.

UPDATE: Monday, Oct. 22 at 4:30 p.m. ET by Tim Keeney

Well, that was quick. It was originally thought that Mannion could miss a large chunk of playing time, but after just two weeks, Mike Riley has stated that the sophomore QB will make his return this Saturday (via the Corvallis Gazette-Times' Cliff Kirkpatrick):

Riley made it official after Monday's practice, Mannion is the starter Saturday. More later.

It appears as though Oregon State fans will have to get used to Cody Vaz. The junior certainly has the talent to step in for Mannion under center, but his lack of experience won't put to rest many concerns.

---End of update---

The Beavers' 4-0 start to the season will be tested this week when they travel to Provo to take on a solid 4-2 BYU squad, and to make things worse, they'll be without Mannion (according to head coach Mike Riley, via KEZI 9 Sports' Stephen Nelson):

BREAKING: Mike Riley announces QB Sean Mannion will have surgery on his knee. Out an undisclosed amount of time. #GoBeavs

Mannion was on his way to a huge season: 63.3 completion percentage, 1,358 passing yards (339.5 per game), seven touchdowns and four interceptions. Extrapolate those numbers out to a full season, and the youngster would throw for 5,432 yards and 21 touchdowns.

Not bad.

To be fair, Oregon State has other weapons capable of stepping up in Mannion's stead.

Christian Petersen/Getty Images

Freshman running back Storm Woods, who has totaled 341 rushing yards on just under five yards per carry, looks like a future star. Veteran wideout Markus Wheaton is one of the more underrated offensive players in the league. And if all else fails, don't forget that Oregon State's defense is ranked 18th in the country in terms of points and 34th in terms of yards.

Still, though, it's hard not to make a big deal out of this.

How many games will the Beavers win this season?

4-56-78-910+Submit Votevote to see results

How many games will the Beavers win this season?

4-5

3.5%

6-7

22.4%

8-9

44.0%

10+

30.1%

Total votes: 339

The Beavers will be going from the second-most prolific QB in the Pac 12 (in terms of yards per game) to junior Cody Vaz, who has completed 35 percent of his 17 career collegiate pass attempts.

Although Vaz impressed during spring and fall camps, it's hard for someone with such little experience to jump right into the lion's den and continue leading a Top-10 team to victories.

After BYU, the Beavers host Utah, travel to Washington and host Arizona before going to Stanford to take on the Cardinal.

It's unknown how long Mannion will be sidelined, but if he misses those games, the Beavers are going to be in a world of trouble.